1. Field of the Invention
The present invention relates to a chromatography method and a chromatography kit which make it possible to detect an object analyzed with high sensitivity and at a high S/N ratio (ratio of signals to noise).
2. Description of the Related Art
Among immunoassays, an immunochromatography method is frequently used since this method can be handled easily and makes it possible to measure substances in a short time. As immune reactions used in the immunochromatography method, a competitive reaction and sandwich-type reaction are widely used. Among the reactions, the sandwich-type reaction is mainly used in the immunochromatography method, and typically, the following operation is performed to detect a test substance consisting of antigens in a sample. First, fine particles, which have been sensitized with antibodies against the antigens as the test substance, are immobilized in the form of solid-phase fine particles onto insoluble carriers, or alternatively, the aforementioned antibodies are directly immobilized onto insoluble carriers, whereby insoluble carriers having a reaction site where the antibodies react with the antigens as the test substance are formed. Meanwhile, fine labeling particles are sensitized with antibodies that can bind specifically to the test substance so as to prepare sensitized fine labeling particles. The sensitized fine labeling particles are made to move on the insoluble carriers together with the sample containing the test substance. By the above operation, the antibodies having been immobilized to the reaction site formed in the insoluble carriers function as an immobilized reagent, and the sensitized fine labeling particles bind specifically to the immobilized reagent via the antigens as the test substance. As a result, by determining whether there is a signal that is generated when the sensitized fine labeling particles are trapped in the reaction site or by judging the intensity of the signal by visual observation, it is possible to decide whether the sample contains the test substance or to measure the amount of the test substance.
In the immunochromatography method, in order to avoid a problem (false negative) in which antigens are not detected due to low sensitivity, a method of amplifying detection signal is implemented in some cases. As the signal amplification method, there is a method of using enzymes such as alkaline phosphotase or peroxidase as a label. Moreover, in some cases, antigens are detected by sensitizing labels selected from a group consisting of colloidal metal labels and metal sulfide labels with a silver ion-containing compound and a reductant for the silver ions (silver amplification).
JP2009-216695A discloses an immunochromatography method in which a washing solution is developed such that an angle of 45° to 170° is formed between the developing direction of a test substance and the developing direction of the washing solution. The document discloses that silver amplification may be performed, and bovine serum albumin (BSA)-containing phosphate buffered saline (PBS) is used as the washing solution.
Meanwhile, JP1994-167499A (JP-H06-167499A) discloses a solid-phase immunoassay in which a solution containing guanidine hydrochloride, thiocyanate, or urea is used to remove or wash antigens to be measured, antibodies to be measured, and/or unreacted labels. JP1995-159406A (JP-H07-159406A) discloses a method of washing labeling substances, which have been non-specifically adsorbed onto a reaction container and carriers for making immune components to be in a solid-phase, with a washing solution containing a sugar-based nonionic surfactant and chaotropic ions. JP1991-2662A (JP-H03-2662A) discloses an immunoassay system in which a chaotropic solution is used as a washing solution. JP1999-146783A (JP-H11-146783A) discloses a ribonucleic acid extraction method in which foreign substances which are not nucleic acids and have been non-specifically adsorbed onto carriers are washed with a solution containing a chaotropic substance.